First make the vegetable stock. Heat 1-2 tsp. olive oil in a stockpot. Add the leek and fennel trimmings, onion, carrot, and celery and let them sweat down for a couple of minutes. Cover with 2 quarts of cold water and add the parsley, garlic, about 10 peppercorns, and a few pinches of salt. Bring to a boil, then reduce to a simmer. Cook for 20-30 minutes, then strain. This will make about twice as much stock as you'll need for the soup. Freeze the rest and save it for your next batch of soup, polenta, or risotto.

When your stock is almost finished, get started on the soup. Heat 1 Tbsp. butter and 1 Tbsp. olive oil together in a Dutch oven or soup pot. Add the leeks and fennel, season with salt, and sauté until softened, about 10 minutes. Add the potatoes and stock to cover (4-5 c.). Season with salt, bring to a boil, then reduce to a simmer. Cook until the fennel is very tender and the potatoes are beginning to fall apart, 30-40 minutes.

Allow the soup to cool briefly, then puree it using an immersion blender or food processor. You can puree the soup until it is perfectly smooth or leave it a little chunky as I did. If it is too thick, thin it out with a bit more stock. Taste. Season with additional salt, if necessary, freshly ground black pepper, and tsp. or 2 of fresh lemon juice. Return to the stove and gently reheat.

Meanwhile, smash the black olives into a paste using mortar and pestle or a mini food processor. Stir in a couple of Tbsp. olive oil to loosen it.

Divide the soup between bowl. Dollop a spoonful of the olive puree in the center and top with a few of the wispy fennel fronds.

Recipe by strawberryplum at http://www.strawberryplum.com/potato-fennel-leek-soup-with-olive-tapenade/